It is frequently necessary to transport elderly or disabled bathers into a bathtub by means of a bath lift located in the tub. Water powered operation is a safe means of operation because no electricity is required, and it is convenient because the water source is already provided in the bathtub. The lift requires only that the person to be bathed enter the lift chair as it sits over the edge of the bathtub. The chair carrying that individual is rotated over the tub and the lift then does the work of lowering him into the tub or raising him up for showering and exiting the tub.
In order not to mar the bath tub, and enable the lift system to be readily installed and removed, it is common practice to provide the base unit with suction cups on the ends of legs. The suction cups, usually four, adhere to the base of the bath tub.
There has existed heretofore a serious problem of slippage of such a lift device relative to the tub during use by the bather. When the chair is swung out to one side, the cantilever action can cause the suction cups to slide sideways across the base, since suction cups do not provide good resistance to lateral or shear loads. This problem can cause potentially serious injury to the person being bathed, and often has necessitated the use of additional persons to assist with the bathing.
As a result of the problem of slippage of the bath lift relative to the bath tub, various attempts have been made to stabilize the bath lift to the tub by use, for example, of stabilizer bars extending from the base and affixed to the sides of the tub by means of suction cup devices. However, the basic mode of instability still remains. A cantilevered load applied when the chair is swung out, tends to rotate the whole unit about a longitudinal axis approximately in the centre of the bath tub. This applies shear loads to the suction cups which tend to slip. Thus, this stabilization scheme still does not provide sufficient security against rotation of the bath lift mechanism due to slippage of the suction cups along the wall of the tub as the load is being applied. Prevention of such rotation and slippage is very important as, for elderly or physically handicapped users, any small degree of instability can throw them from the lift, causing injury, or drowning as a result of immersion of the person's face which the person cannot prevent.